Hydraulic lash adjuster



United States Patent() 3,142,290 HYDRAULIC LASH ADIUSTER Kenneth W. Lasher, Wheaton, Ill., assignor to Standard `crew Company, Bellwood, lll., a corporation of New ersey Filed lItaly 13, 1962, Ser. No. 209,542 9 Claims. (Cl. 12S-9u) This invention relates to improvements in hydraulic tappets and has for a primary purpose a means for preventing pump-up of a hydraulic tappet at high engine r.p.m.

Another purpose is a hydraulic tappet of the type described having a vent passage which opens into the tappet cylinder oil chamber at high engine r.p.m.

Other purposes will appear in the ensuing specification, drawings and claims.

The invention is illustrated diagrammatically in the following drawings wherein:

FIGURE 1 is an axial section through a tappet of the type described,

FIGURE 2 is a plan view, with portions cut away, showing a modied form of tappet, and

FIGURE 3 is a plan View, similar to FIGURE 2, illustrating yet a further form of tappet.

In FIGURE 1, the tappet cylinder is indicated at and may have the conventional open upper end 12. Mounted for reciprocation within the cylinder 10 is a plunger indicated generally at 14 and having an oil chamber 16. The upper end of the chamber 16 may be closed by a valve element or cap 1S having a hemispherical recess 20 to receive the ball end of a push rod, not shown. A suitable snap ring 22, as is conventional, may complete the upper end of the tappet.

The plunger 14 may have one or more ports 24 which open into an annular space defined by opposed annular grooves 26 on the outside surface of the plunger and 28 on the inside surface of the cylinder. The space dened by these two annular grooves is in communication with the exterior of the cylinder through a port or passage 30 in the cylinder wall.

The lower end of the plunger may be open and a valve element 32, seated against lower surface 34 of the plunger, may be used to control the flow of oil from the chamber 16 to a cylinder oil chamber 36. Within the cylinder oil chamber 36 is a spring 38, normally biasing the cylinder and plunger in opposite directions. The valve element 32 may be loosely held in position by a retainer 40, the upper end of which is held in position by the top of the spring 38 and a check valve spring 41. The retainer 40 may have an upper outwardly extending flange 42 which seats against a shoulder 44 on the plunger.

At times, particularly at high engine speeds, the charnber 36 will receive an excessive amount of oil from chamber 16 and the pressure in this chamber will build up to such a degree that it will force the plunger 14 in an upward direction. The plunger may be pumped up until the retaining ring stops its upward movement. This in turn moves the push rod, rocker arm and engine valve to a point where the valve cannot close. Power is lost and the valve train is in a pumped-up condition. This condition will exist until engine speed is reduced and the excess volume of oil and pressure in the tappet below the plunger is allowed to escape and the plunger returns to its normal operating position.

To prevent engine pump-up it is necessary to bleed olf the pressure within the chamber 36. Accordingly, I have placed a port or passage 46 in the cylinder and have reduced the outer diameter of the plunger portion adjacent the chamber 36, as at 48. In effect, the re- 3,142,296 Patented `lilly 28, 1964 ice duced portion of the plunger forms a passage between the oil chamber 36 and port 46 when the plunger has been moved upwardly. Normally at low engine speeds, the passage or reduced portion 48 will not be in communication with the port 46 as the tappet is initially set for the position of FIGURE l. However, when the pressure in the chamber 36 increases, the plunger will be forced upwardly so that port 46 will no longer be closed by the plunger but will be in communication with the chamber 36. Oil pressure within the chamber is then bled out or vented through the reduced portion 4S and the passage 46.

In order to provide a vent arrangement with no obstruction, it is desirable that port 46 open into an area which can readily pass the oil. Accordingly, I have formed an annular axially extending groove 50 in the outside surface of the cylinder, this groove extending from the port 30 down to and past the port 46. In this way, oil being vented through port 46 can flow into annular axial groove 50.

FIGURE 2 illustrates a form of the invention in which a separate groove, indicated at 52, is provided for port 46. The other details of the tappet in FIGURE 2 are substantially the same as that illustrated in FIGURE 1. The normal oil feed groove 50 is located higher relative to the cam face and therefore a separate groove 52 is necessary for the bleed-olf port 46.

FIGURE 3 illustrates yet a further form of the invention in which the outer surface of the cylinder 10 has a iiattened area 54 which connects port 46 with the oil feed groove 50. In this case the oil feed groove 50 does not have to extend as far axially as the groove 50 in FIGURE l. In any event, it is important to provide some means for removing the oil after it passes through port 46.

The use, operation and function of the invention are as follows:

This invention relates to an anti-pump-up tappet and in particular to a means for bleeding off oil pressure in the cylinder oil chamber in a tappet. Pump-up normally occurs at high engine speeds and the result of pump-up is that the push rod, rocker arm and engine valve are moved upwardly to a point where the valve cannot close. Power is lost and the engine docs not operate properly. In addition to permitting the engine to effectively operate at a higher rpm., -a tappet of the type described has the advantage of providing a safety device to keep the engine valve from hitting the piston and possibly wrecking the engine. A hydraulic tappet of this type is primarily for those who wish to operate their engines above the present maximum designed speeds and power settings and still have all the advantages of a standard hydraulic unit when operating at normal engine speeds.

When a tappet of the type described is initially installed, the bottom edge of the outside diameter of the plunger should be just beyond the port 46 so that the port is normally closed. Any load applied to the top of the plunger, to the plunger cap 18, will move the plunger down in relation to the body. Below this initial position and during normal engine operation, the tappet functions as any other hydraulic tappet. As the engine speed is increased to the point where pump-up or nofollow conditions exist, the plunger tries to move up in relation to the body or cylinder, thereby extending the length of the valve train parts. The slightest upward movement of the plunger allows the bottom edge of the reduced portion or passage 48 to uncover port 46 and so place the port in communication with the chamber 36. The high pressure oil trapped below the plunger then escapes out through port 46 and, as shown in FIG- URES 1 and 3, to the oil groove 50'. This stops the upward movement of the plunger and, as the load is re-applied, the plunger moves back to its original position along with the remaining portions of the valve train. This allows the engine valve to close and the engine to produce another power cycle.

Although as shown the means for bleeding off the pressure in the chamber 36 comprise a port in the cylinder and a reduced portion or passage in the plunger, the invention should not be limited to this particular conliguration. What is important is to provide passage means between the chamber 36 and the exterior of the cylinder which are normally closed, but open when the pressure from the chamber 36 becomes suiciently high to move the piston or plunger upwardly.

Whereas the preferred form of the invention has been shown and described herein, it should be realized that there are many modifications, substitutions and alterations thereto within the scope of the following claims.

I claim:

1. A hydraulic tappet including a hollow cylinder closed at one end, a plunger mounted for reciprocation within said cylinder, an oil chamber in said plunger, an oil passage through said cylinder and plunger opening into said chamber, `an oil chamber in said cylinder and yielding means in said cylinder oil chamber biasing said plunger and cylinder in opposite directions, the end of said plunger adjacent said cylinder oil chamber being open and a valve in said opening controlling the flow of oil to said cylinder oil chamber, and passage means, closed by said plunger during a normal range of relative axial displacement between the cylinder and plunger, connecting the cylinder oil chamber with the exterior of said cylinder, movement of said plunger in a direction outwardly of said cylinder, at an excessive range of relative axial displacement between the cylinder and plunger, opening said passage means.

2. The structure of claim l further characterized in that said passage means includes a port in said cylinder, said port being closed by said plunger during a normal range of relative axial displacement between the cylinder and plunger.

3. The structure of claim 2 further characterized in that said passage means includes a reduced portion at the end of said plunger adjacent said cylinder oil chamber, said plunger reduced portion being placed in communication with said port by movement of said plunger in a direction outwardly of said cylinder.

4. The structure of claim 1 further characterized in that said passage means includes a port in said cylinder and a passage in the end of said plunger adjacent said cylinder oil chamber, said plunger closing said port during a normal range of relative axial displacement between the cylinder and plunger, movement of said plunger in a direction outwardly of said cylinder, at an excessive range of relative axial displacement between the cylinder and plunger, placing said port in communication with the plunger passage.

5. The structure of claim 1 further characterized by and including a recessed area in the outer surface of said cylinder connecting said passage means with the oil passage through the cylinder and plunger.

6. The structure of claim 5 further characterized in that said recess includes an annular and axially extending groove in the outer surface of said cylinder.

7. The structure of claim 5 further characterized in that said recess includes an axially extending flattened portion on the outer surface of said cylinder.

8. The structure of claim 1 further characterized by and including an annular groove in the outer surface of said cylinder, said passage means opening into said annular groove.

9. A hydraulic tappet including a hollow cylinder closed at one end, a plunger mounted for reciprocation within said cylinder, an oil chamber in said plunger, an oil passage through said cylinder and plunger opening into said chamber, an oil chamber in said cylinder, the end of said plunger adjacent said cylinder oil chamber being open and a valve in said opening controlling the ow of oil to said cylinder oil chamber, and passage means, closed by said plunger during a normal range of relative axial displacement between the cylinder and plunger, connecting the cylinder oil chamber with the exterior of said cylinder, movement of said plunger in a direction outwardly of said cylinder, at an excessive range of relative axial displacement between the cylinder and plunger, opening said passage means.

References Cited in the le of this patent UNTTED STATES PATENTS Re. 24,506 Humphreys July 22, 1958 2,599,886 Bergmann lune 10, 1952 2,942,595 Bergmann et al. June 28, 1960 2,943,611 Dadcl July 5, 1960 

1. A HYDRAULIC TAPPET INCLUDING A HOLLOW CYLINDER CLOSED AT ONE END, A PLUNGER MOUNTED FOR RECIPROCATION WITHIN SAID CYLINDER, AN OIL CHAMBER IN SAID PLUNGER, AN OIL PASSAGE THROUGH SAID CYLINDER AND PLUNGER OPENING INTO SAID CHAMBER, AN OIL CHAMBER IN SAID CYLINDER AND YIELDING MEANS IN SAID CYLINDER OIL CHAMBER BIASING SAID PLUNGER AND CYLINDER IN OPPOSITE DIRECTIONS, THE END OF SAID PLUNGER ADJACENT SAID CYLINDER OIL CHAMBER BEING OPEN AND A VALVE IN SAID OPENING CONTROLLING THE FLOW OF OIL TO SAID CYLINDER OIL CHAMBER, AND PASSAGE MEANS, CLOSED BY SAID PLUNGER DURING A NORMAL RANGE OF RELATIVE AXIAL DISPLACEMENT BETWEEN THE CYLINDER AND PLUNGER, CONNECTING THE CYLINDER OIL CHAMBER WITH THE EXTERIOR OF SAID CYLINDER, MOVEMENT OF SAID PLUNGER IN A DIRECTION OUTWARDLY OF SAID CYLINDER, AT AN EXCESSIVE RANGE OF RELATIVE AXIAL DISPLACEMENT BETWEEN THE CYLINDER AND PLUNGER, OPENING SAID PASSAGE MEANS. 